Air-hydraulic press



Feb. 4, 1969 OLIVER ET AL 3,425,219

AIR-HYDRAULIC PRESS Filed Aug. 21, 1967 wvwy United States Patent 3,425,219 AIR-HYDRAULIC PRESS Henry N. Oliver and Carl H. Morris, Rockford, 111., as-

signors of fifty percent each to Henry N. Oliver and Carl H. Morris, Rockford, Ill.,

Filed Aug. 21, 1967, Ser. No. 662,005

U.S. Cl. 60-52 12 Claims Int. Cl. F15b 15/18, 7/00 ABSTRACT OF THE DISCLOSURE An air-hydraulic press in which a movable ram piston is hydraulically actuated by a reciprocatory hydraulic pump formed in the movable ram piston and driven by an air-operated piston. Hydraulic fluid is supplied to the hydraulic pump from a reservoir having a floating wall to accommodate changes in volume in the reservoir.

Background of the invention The invention relates to an air-hydraulic press. Such presses generally include an hydraulically operated ram and a reciprocating hydraulic pump driven by an airoperated piston. The presses are arranged to effect pressure multiplication whereby a relatively low air pressure acting on the air piston delivers substantially higher bydraulic pressure from the pump to the hydraulic ram.

Summary of the invention The air-hydraulic press includes a ram cylinder and ram piston, a pump cylinder and pump piston, and an air cylinder and air-operated piston, and the press is constructed and arranged so that the ram cylinder is formed in the pump piston with a consequent reduction in the over-all number of parts in the press. The pump piston is connected to the airoperated piston for actuation thereby, and the pump is advantageously arranged to deliver fluid under pressure to a ram working chamber at the end of the ram piston opposite the air-operated piston so that, when the pump piston moves in one direction in the pump cylinder to discharge fluid to the ram piston, the ram piston moves in a relatively opposite direction. An hydraulic reservoir is provided for supplying. fluid to the pump piston and ram, and the reservoir is advantageously located at the side of the ram piston opposite the ram working chamber. The reservoir is provided with a movable or floating wall to accommodate changes in volume in the reservoir during operation of the press and, advantageously, the movable wall is located to separate the hydraulic reservoir from the air cylinder whereby pressure applied to the air cylinder to retract the pump piston is also applied through the movable wall to the hydraulic fluid in the reservoir to pressurize the fluid in the reservoir to aid in filling the pump cylinder during retraction of the pump piston. The ram cylinder, reservoir and air cylinder can conveniently be formed in a single casing. In the preferred embodiment illustrated, the press is especially adapted for use as a punch in which the end of the casing means supports a die member and a punch member is connected to the movable ram and is drawn through the workpiece to punch an opening of the desired size and shape in the workpiece.

An important object of the present invention is to provide an air-hydraulic press which is of simple and economical construction.

A more particular object of this invention is to provide an air-hydraulic press in which the hydraulic pump is formed in the ram piston with a consequent reduction in the over-all number of parts in the press.

Another object of this invention is to provide an airhydraulic press in which the hydraulic reservoir includes a floating wall to accommodate changes in volume in the reservoir during operation of the press and so arranged that pneumatic pressure applied to the air-operated piston during retraction of the pump piston operates to also pressurize the fluid in the reservoir to aid in filling the pump cylinder.

A further object of this invention is to provide an airhydraulic press in accordane with the foregoing object and wherein the fluid pressure on the end of the ram piston opposite the ram working chamber is reduced to substantially atmospheric pressure during the working stroke of the pump piston so that the full pump discharge pressure is effective for moving the ram.

These, together with other objects and advantages of this invention, will be more readily understood from the following description when taken in connection with the accompanying drawings, wherein:

FIGURES 1 and 2 are longitudinal sectional views through the air-hydraulic press showing the parts in different moved positions; and

FIG. 3 is a fragmentary end elevational view of the air-hydraulic press.

The preferred embodiment of the air-hydraulic press illustrated in the accompanying drawings is specifically designed for use as a portable press for punching holes in a workpiece, it being apparent that the press could be adapted for other punching or pressing operations and could be incorporated in a stationary press if desired. In the embodiment illustrated, the press includes a casing means 10 conveniently in the form of a unitary casing having a ram cylinder 11, an air cylinder 12 and a reservoir cylinder 13 advantageously located intermediate the ram cylinder and the air cylinder. In the form shown the reservoir cylinder has the same diameter and is coaxial with the ram cylinder so that both can be formed as a single bore in the casing. The air cylinder is preferably of a larger diameter than the ram cylinder and is conveniently formed as a counterbore disposed coaxial with the ram and reservoir cylinder. The end of the air cylinder is closed by a head 15 removably attached to the casing by fasteners 16, and a handle 17 is conveniently attached to the head to facilitate manipulation of the press when used as a portable unit.

A ram piston 18 is slidably disposed in the ram cylinder 11 and has a sliding seal therewith conveniently formed by an O-ring 19 disposed in a groove 21 in the ram piston. A ram working chamber 26 is formed at one end of the ram piston, and in the preferred embodiment, the ram piston has a reduced extension 22 on the end of the ram remote from the air cylinder, which reduced extension is slidably received in a reduced diameter portion 23 of the casing and is sealed thereto as by an O-ring 24- disposed in a groove 25 in the reduced diameter portion 23. The ram piston 18 forms the ram working chamber 26 in the ram cylinder at the outer end of the ram piston as shown in FIGS. 1 and 2, and pressure in the ram working chamber is applied to an area on the outer end of the ram piston corresponding to the dififerential area between the reduced extension 22 and the outer diameter of the ram piston 18.

An air piston 31 is slidably disposed in the air cylinder 12 and has a sliding seal therewith formed as by an O- ring 32 disposed in a groove 33 in the air piston. The air piston separates the air cylinder 12 into first and second air working chambers 35 and 36 at relatively opposite sides of the' air piston, the relative volumes of which chambers vary as the piston moves in the air cylinder.

The air-operated piston 31 operates an hydraulic pump for pumping fluid to the ram working chamber. The hydraulic pump includes a cavity or cylinder 41 herein generally referred to as a pump cylinder formed in the ram piston 18 and extending into the end of the ram piston adjacent the air cylinder. The pump cylinder is made relatively long to accommodate not only the full stroke of the air piston but also the full stroke of the movable ram pisto 18 and, for this purpose, the ram piston is formed with a second reduced extension 42 on the end adjacent the air cylinder. A pump piston 43 is connected to the air piston for movement therewith and, as shown, is conveniently formed integrally with the air piston. The pump piston extends into the pump cylinder 41 and has a sliding seal therewith to form a pump chamber in the pump cylinder at the inner end of the pump piston. In the embodiment illustrated, the seal is formed by an O-ring 44 disposed in a groove 45 on the pump piston, it being understood that the seal could alternatively be formed by an O-ring carried by the ram piston and having a sliding seal with the pump piston 43.

Fluid is supplied to the hydraulic pump from a fluid reservoir and, as previously described, the fluid reservoir is advantageously formed in the reservoir cylinder located between the ram cylinder and the air cylinder. A movable wall or floating piston 51 is slidably disposed in the reservoir cylinder 13 and sealed thereto as by an O-ring 52 disposed in a groove 53 on the floating piston 51. The pump piston 43 extends through an opening 54 in the floating piston 51 and is sealed thereto as by an O-ring 55 disposed in a groove 56 in the floating piston. The floating piston is free to move along the reservoir cylinder 13 to accommodate changes in volume in the reservoir that occur during operation of the press, and the floating piston separates the reservoir chamber 58 from the second air working chamber 36. In the preferred embodiment illustrated, the inner end of the ram piston 18 forms one end of the reservoir 58 and is exposed to the fluid pressure in the reservoir. Passage means are provided for passing fluid from the reservoir 58 to the pump cylinder 41 during retraction of the pump piston and for discharging fluid from the pump cylinder to the ram working chamber 26 When the pump piston is extended. The pump passages are advantageously formed in the ram cylinder and, in the embodiment illustrated, the passages include a generally radially extending bore 61 which communicates with the inner end of the pump cylinder 41 and which is counterbored at 62 adjacent its outer end to define a valve seat 63. A check valve 64, herein shown of the ball type, is disposed in the counterbore 62, and the ram piston is peripherally recessed at 65 to communicate the outer end of the counterbore with the ram working chamber 26. The check valve 64 is arranged to open for flow from the pump cylinder 41 to the ram working chamber 26 and to close to prevent return flow. In the embodiment illustrated, the counterbore 62 is arranged to define a somewhat restricted flow passage around the check valve 64 so that, when the fluid begins to flow in the reverse direction from the ram working chamber 26 to the pump cylinder 41, the check valve is urged toward the seat 63 to block flow. Alternatively, a relatively light spring can be provided to normally urge the check valve 64 to its closed position. Another passage 67 communicates with the passage 61 between the seat 63 and the pump cylinder and is counterbored at its outer end to receive an apertured valve seat member 68 conveniently threaded into the counterbore. A check valve 69 is disposed in the inner end of the counterbore and is movable away from the valve seat member to allow flow from the reservoir to the pump cylinder and to close to prevent return flow. The counterbore is also preferably dimensioned with relation to the diameter of the check ball 69 so as to produce a pressure drop on the fluid flowing thereby to hydraulically urge the check valve 69 to its closed position when hydraulic fluid is discharged from the pump cylinder. The passage 67 is conveniently offset from the axis of the counterbore so as to prevent the ball check valve 69 from seating against the passage 67 during flow from the reservoir to the pump cylinder.

When the air piston 31 is reciprocated, the pump piston 43 will move relative to the pump cylinder to alternately draw a charge of hydraulic fluid from the reservoir 58 into the pump cylinder and to discharge the hydraulic fluid from the pump cylinder to the ram working chamber 26. A valve and passage arrangement is provided for returning fluid from the ram working chamber 26 back to the reservoir after the completion of the punch operation. or this purpose, a passage 71 is formed in the casing 10 to communicate with the ram chamber 26, and a passage 72 extends from the passage 71 to a valve 73 mounted on the casing. The valve includes a body 74 conveniently threaded into the casing and having an inlet 75 and an outlet 76 and a movable valve member 77 which normally blocks flow from the inlet to the outlet and which is movable to an open position to pass fluid from the ram working chamber 26 back to the reservoir 58. As will be seen, the passages 71 and 72 can conveniently be formed by drilling or coring the casing, and the ends of the passages are closed by plugs 78, as is conventional.

Air under pressure from a source (not shown) such as the usual plant air supply is alternately applied and exhausted from the air working chambers 35 and 36 to reciprocate the air piston and operate the hydraulic pump. In the embodiment shown, a manually operable valve is provided for controlling the application of air to the air working chamber, it being understood that an automatic cycling valve could also be employed if desired. The valve 85 is conveniently mounted on the casing and includes a valve housing 86 having a valve bore 87 therein. An inlet passage 88 is connected as through a line 89 to the air supply, and controlled outlet ports 91 and 92 communicate with the valve bore and through passages 93 and 94 with the air working chambers 36 and 35, respectively. Exhaust ports 95 and 96 also communicate with the valve bore at points spaced from the inlet and from the control outlets, and a spool valve member 98 is slidably disposed in the valve bore and has spaced grooves 98a and 98b operative in one position, as shown in FIG. 1, to communicate the inlet 88 with the controlled outlet port 91 while communicating the controlled outlet port 92 with one of the exhaust ports 96, and operative in the other position shown in FIG. 2 to communicate the inlet 88 with the controlled outlet port 92 while communicating the controlled outlet port 91 with the exhaust outlet port 95. The spool valve is normally urged to one position against a stop 100 as by a spring 101, and the end of the valve bore is preferably vented as shown at 102. A manually operable knob or handle 103 is provided for operating the valve.

In the embodiment illustrated, the press is used to operate a hole punch. As shown, the end of the casing 10 forms an anvil that supports a hollow die member D. A punch member P is connected through a spindle S to the ram so that when the ram is actuated, the punch is drawn through the workpiece W to punch a hole in the workpiece as shown in FIG. 2. In use, the workpiece must be predrilled to provide an opening 0 for receiving the spindle, and the punch is assembled on the spindle after it has been inserted through the workpiece.

Operation At the beginning of a press operation, the parts are in the position shown in FIG. 1 with the bypass valve 77 closed and with the air control valve 85 in a position applying air pressure from the inlet 88 through passage 91 to the air working chamber 36 to retract the air operated piston 31 and the pump piston 43 therewith. Under these conditions, the air pressure is also applied to the movable wall 51 to pressurize the hydraulic fluid in the reservoir 58. If the ram piston 18 is not in its fully extended position, it can be moved to its fully extended position by opening the valve 77 when valve member 98 is in the FIG. 1 position. When valve 73 is open, the pressure in reservoir 58 and ram working chamber 26 are equalized. However, the area at the left-hand end of the ram piston which is exposed to the pressure in the reservoir is greater than the area at the right-hand end of the ram piston exposed to hydraulic fluid pressure and, when the fluid in the reservoir is pressurized above atmospheric pressure, as occurs when valve member 98 is in the position shown in FIG. 1, the hydraulic pressure acting on the relatively different areas at opposite ends of the ram piston will produce a pressure unbalance to urge the ram piston to its fully extended position (to the right) as shown in FIG. 1. The bypass valve 77 is closed prior to starting the punching operation. The press can then be operated by moving the air control valve spool 98 inwardly to the position shown in FIG. 2 to apply air pressure to the air working chamber 35 and to exhaust air pressure from the air working chamber 36. The pneumatic pressure unbalance on the air piston 31 moves the air piston and the pump piston 43 to their extended position, as shown in FIG. 2, and thereby discharges the hydraulic fluid from the pump cylinder 41 through passage 61 and check valve 64 to the ram working chamber 26. This produces an incremental movement of the ram piston to the left as viewed in FIGS. 1 and 2. During this working stroke of the air piston, the air pressure in the air working chamber 36 is at substantially atmospheric pressure, and this low pressure is transmitted through the movable wall 5'1 to the hydraulic fluid in the reservoir 58 so that, during the working stroke of the pump piston, the inner or lefthand end of the ram piston is subjected to substantially atmospheric pressure. When the spool valve 98 is released and moves to the position shown in FIG. 1, air under pressure is applied to the air working chamber 36 and exhausted from air working chamber 35 to retract the pump piston 43. A charge of hydraulic fluid from the reservoir 58 then flows past check valve 69 and through passages 67 and 61 into the. pump cylinder 41. During retraction of the air-operated piston, the air pressure in air working chamber 36 is transmitted through the movable wall 51 to the hydraulic fluid in the reservoir 58, and this pressurizes the hydraulic fluid to aid in filling the pump cylinder. In this manner, the air control valve can be moved from the position shown in FIG. 1 to the position shown in FIG. 2 and back, to effect reciprocation of the hydraulic pump and produce corresponding incremental movement of the ram piston. As will be seen, the diameter of the air-operated piston 31 is large as compared to the diameter of the pump piston 43 to produce a. relatively high pressure multiplication, and the area on the end of the ram piston which is exposed to the fluid pressure in the ram working chamber 26 is preferably made relatively large as compared to the area of the pump piston so that the total hydraulic thrust produced on the ram piston is very high. Obviously, the relative sizes of the air-operated piston, the pump piston and the working area on the end of the ram piston can be varied to produce the desired thrust on the ram piston with the available air pressure supply. As the ram piston 18 moves to the left during operation of the press, some of the hydraulic fluid in the reservoir 58 is delivered to the ram working chamber. However, this movement of the ram piston also displaces a quantity of hydraulic fluid in the reservoir. In the embodiment illustrated, the effective or working area on the ram piston which is exposed to the fluid pressure in the ram working chamber 26 is substantially less than the effective area at the other end of the ram piston which is exposed to the fluid pressure in the reservoir 58. Consequently, as the ram piston moves to the left, the volume of hydraulic fluid in the reservoir 58 which is displaced by the ram piston is greater than the volume of liquid which is transferred to the ram working chamber 26. The movable wall 51 can then shift to accommodate this change in volume and, in the present case, will move to the left as the ram piston moves to the left, but at a somewhat slower rate than the rate of movement of the ram piston. This is advantageous in that it allows a somewhat greater working stroke of the ram piston before the ram piston engages the movable wall. The movable wall 51 also functions as a stop to limit movement of the ram piston in its working stroke, that is, to the left as viewed in FIGS. 1 and 2. Thus, when the extension 42 on the ram piston .18 engages the movable wall 5'1, the hydraulic reservoir cannot decrease further in volume. Consequently, if the air operated piston 31 is reciprocated in response to actuation of valve after the ram piston engages the wall, the pump piston 43 cannot withdraw further hydraulic fluid from the reservoir and therefore will not discharge additional fluid to the ram working chamber 26. The dimensions of the various parts including the ram piston 18 and movable wall 51 are, of course, selected so that the ram piston only engages the movable wall after the ram piston has been moved through its desired stroke. In order to minimize the over-all size of the apparatus, the movable wall 51 is preferably dish-shaped, as shown at 5111 to receive the reduced end portion 42 on the ram piston, and the air-operated piston is also preferably dish-shaped as shown at 31a to receive the dished portion of the movable wall.

As the ram moves to the left, it of course draws the punch P through the workpiece W to punch a hole in the workpiece. At the completion of the punch or press operation, bypass valve 73 is opened to allow the fluid pressure to return the ram piston to its extended position shown in FIG. 1.

From the foregoing, it will be seen that the several parts can be easily machine and assembled. Since the pump cylinder is formed in the ram piston, a separate pump cylinder is unnecessary so that the over-all num ber of parts is reduced. Moreover, the passageways for communicating the pump cylinder with the reservoir and ram working chamber are markedly simplified. The reservoir having the movable wall is so arranged that the fluid pressure in the air working chamber 36 pressurizes the fluid in the hydraulic reservoir during retraction of the pump piston to aid in filling the pump cylinder and relieves the pressure in the fluid reservoir during the working stroke of the pump piston so that the full discharge pressure of the hydraulic pump is effective for moving the ram.

While in the foregoing there has been shown and described the preferred embodiment of the invention, it is to be understood that minor changes in the details of construction and arrangement of parts may be resorted to without departing from the spirit and scope of the in vention as claimed.

What is claimed as new is:

1. An air-hydraulic press comprising, casing means defining a ram cylinder adjacent one end of the casing means and an air cylinder adjacent the other end of the casing means in fixed relation to the ram cylinder, a movable ram piston slidable in the ram cylinder defining therewith a ram working chamber at one end of the ram piston, ram means connected to the ram piston and extending outside the casing means, an air-operated piston slidable in the air cylinder and defining therewith one air working chamber at one side of the air-operated piston, means defining a reservoir for hydraulic fluid, said movable ram piston having a pump cylinder extending into one end thereof and paralleling the axis of said ram cylinder, a pump piston connected to the air-operated piston for movement therewith and extending into the pump cylinder in the ram piston in sliding seal therewith to define a pump working chamber in the pump cylinder, a first passage means communicating said pump working chamber with said reservoir for flow of hydraulic fluid from the reservoir to the pump working chamber, a second passage means communicating the pump working chamber with said ram working chamber for flow of hydraulic fluid from the pump working chamber to the ram working chamber, and means for applying and exhausting air pressure from said one air working chamber to move the air-operated piston and the pump piston and thereby pump hydraulic fluid from the reservoir to the ram working chamber.

2. An air-hydraulic press according to claim 1 wherein said ram working chamber is at the outer end of said r-am piston opposite said one end into which the pump cylinder extends whereby movement of the pump piston in one direction with the pump cylinder discharges fluid from the pump working chamber to the outer end of the ram piston to urge the latter in a direction opposite said one direction.

3. An air-hydraulic press according to claim 1 wherein said reservoir is located between said ram cylinder and said air cylinder and includes a movable wall separating the air cylinder from the reservoir to accommodate changes in volume of hydraulic fluid in the reservoir.

4. An air-hydraulic press according to claim 1 wherein said means defining an hydraulic reservoir includes a reservoir cylinder intermediate said ram cylinder and said air cylinder and a reservoir piston slidable in said reservoir cylinder and defining said reservoir with said one end of the ram piston, said reservoir piston defining a second air working chamber with said air cylinder and the other side of the air-operated piston, said pressure applying means being operative to alternately apply air pressure to said first and said second air working chambers.

5. An air-hydraulic press according to claim 4 wherein said reservoir cylinder is coaxial with and has the same diameter as said ram cylinder.

6. An air-hydraulic press according to claim 1 wherein said first and second passage means include check valve means located in said ram piston.

7. An air-hydraulic press comprising, casing means defining a ram cylinder adjacent one end of the casing means; a reservoir cylinder intermediate the ends of the casing means and an air cylinder adjacent the other end of the casing means in fixed relation to the ram cylinder, a ram piston slidable in the ram cylinder and having a reduced portion on one end thereof in sliding engagement with the casing means to form a ram working chamber at said one end of the ram piston, an air-operated piston in the air cylinder separating the latter into first and second air working chambers at relatively opposite sides of the air-operated piston, a reservoir piston slidable in the reservoir cylinder and having one side exposed to the air in the second working chamber and the other side exposed to the hydraulic fluid in the reservoir cylinder, said ram piston having a pump cylinder extending into the end thereof adjacent the air cylinder, a pump piston connected to said air-operated piston and extending through said reservoir piston into said pump cylinder in sliding seal there-with to form a pump working chamber in the pump cylinder, at first passage means communicating said pump working chamber with said reservoir and having valve means operative to open for flow from the reservoir to the pump working chamber and to close to prevent return flow, a second passage means communicating said pump working chamber with said ram working chamber and having valve means operative to open for flow from the pump working chamber to the ram working chamber and to close to prevent return flow, and means for applying air pressure alternately to said first and second air working chambers to reciprocate said air-operated piston and the pump piston connected thereto.

8. An air-hydraulic press according to claim 7 wherein said valve means are on said ram piston.

9. An air-hydraulic press according to claim 7 wherein said hydraulic cylinder has the same diameter as said ram cylinder.

'10. An air-hydraulic press according to claim 7 wherein said casing means comprises a one-piece housing in which said ram cylinder, hydraulic cylinder and air cylinder are coaxial bores.

11. An air-hydraulic press according to claim 7 wherein said reduced portion and ram working chamber are on the end of the ram piston opposite the end of the ram piston into which the pump cylinder extends whereby hydraulic fluid discharged from the pump cylinder into the ram cylinder when the pump piston moves in one direction into the pump cylinder causes movement of the ram piston in a relatively opposite direction.

12. An air-hydraulic press according to claim 11 wherein said ram piston has means thereon engageable with the reservoir piston when the ram piston reaches the end of its stroke.

References Cited UNITED STATES PATENTS 2,324,149 7/1943 Gray -545 2,844,978 7/1958 Wyland et a1 60-52 3,266,415 8/1966 Palmer 60-52 EDGAR W. GEOGHEGAN, Primary Examiner.

U.S. Cl. X.R. 60-545. 

